Although canvas image planes and animation image planes are slightly different, they are both image planes, and you can easily convert an animation image plane to a canvas image plane. When you convert an animation image plane to a canvas image plane, the animation image plane’s image file becomes an image layer in the canvas image plane. You can then sketch on it.

See Introduction to canvas and image planes.

You can also convert a canvas image plane to an animation image plane. When you convert a canvas image plane to an animation image plane, Alias first merges the background layer and all image layers (and shape layers) in the canvas image plane into a single image layer (see Merge image layers), and then saves the image as a separate file (see Name a canvas plane).